Fully Coupled DNS Study of Flow Separation Control over MAV with Flexible Lifting Surfaces

ABSTRACT: The objective of this SBIR project is to develop and demonstrate a first-principles-based Direct Numerical Simulation (DNS) tool for the study of flow separation control over flexible lifting surfaces of Micro Air Vehicles (MAVs). The Phase I effort successfully adapted and validated a DoD open source, CoBi, for multiple DNS cases involving transition to turbulence, flow separation, and coupling with flexible surfaces. The fully coupled computational tool uses a DNS-based Navier-Stokes solver and a non-linear large deformation Finite Element-based structural solver to capture the flow physics around a flexible surface down to the Kolmogorov scale. The Phase II effort will involve several key modeling improvements including: higher order spatial and temporal schemes, turbulent Reynolds-stress-based solution adaptation, sliding grids, and a non-inertial reference frame. The aeroelasticity of an AFRL Generic MAV and its mass properties, aerodynamic coefficients, and stability derivatives will be analyzed using the coupled DNS-structural tool with the enhanced Phase II capabilities to complement an ongoing AFRL/MN MAV research effort. A mini propulsive wing with crossflow fan will be studied using the sliding grid and solution adaptation capabilities to predict flow separation and transition to turbulence at high angles of attack. With these new functionalities, the CoBi code could be used for wide range military applications in DoD, as well as commercial applications in civil aviation industry. BENEFIT: A capability to accurately predict and control the flow separation over a flexible lift surface of an MAV can lead to many potential commercial applications of MAV. The designed MAV can be used in an urban warfare environment to conduct reconnaissance in areas not accessible to larger aircraft, such as areas within buildings, to identify and segregate military targets versus areas having high civilian concentrations. It can also be used in environmental and traffic monitoring, countering drug trafficking, accident assessment, and wildlife/land management. Other applications include inspecting high elevation monuments, monitoring risk of first fires, and more generally interventions in constrained and hazardous environments, where it would be dangerous to send a human agent.